1. Field of the Invention
The present invention has subject for removing natural oxide layer on the substrate with a metallic net, which draws hydrogen ions. Since the metallic net draws hydrogen ions, hydrogen radicals impact the substrate not the metallic net, thereby removing the natural oxide layer.
2. Discussion of the Related Art
Among manufacturing processes of a semiconductor device, in a growth process of a silicon epitaxial layer, which is carried out under a relatively low temperature, no matter how thin an oxide layer including impurities may be formed on a substrate for forming the silicon epitaxial layer, it is hard to get a high-quality epitaxial layer. This is why the oxide layer including impurities causes a defect such as dislocation and stacking fault. Therefore, a process of removing the oxide layer is a prerequisite for growth of the silicon expitaxial layer.
The process of removing the oxide layer includes two steps. In a first step, a semiconductor substrate including a natural oxide layer thereon is dipped into a hydrogen fluoride (HF) solution, thereby first wet-etching the natural oxide layer. And the semiconductor substrate is washed with de-ionized water to remove the HF solution on the natural oxide layer, and is dried in a spin drier or a drier using isopropyl alcohol. However, in the first step, another natural oxide layer of about 2 angstroms to about 6 angstroms may be formed on the semiconductor substrate again. Therefore, in a second step, the semiconductor substrate is in-situ pre-cleaned in a plasma apparatus for growing a silicon expitaxial layer, thereby removing the natural oxide layer.
FIG. 1 is a schematic view showing an apparatus for a related art in-situ pre-cleaning of a semiconductor substrate.
As shown in FIG. 1, a semiconductor substrate 130, which has a natural oxide layer thereon, is disposed on a susceptor 110 within a processing chamber 100. A plasma electrode 120 is situated on a bell jar that is the upper part of the processing chamber 100, and is connected to a power supplying system 125 to be supplied with electric power for generating plasma. At this time, the susceptor 110 is grounded, and a hydrogen gas (H2) is provided in the processing chamber 100 through the gas injector 140. Plasma comprising hydrogen ions (H+), electrons and radicals is generated from the hydrogen gas, and the hydrogen ions collide against the natural oxide layer on the semiconductor substrate 130, thereby removing the natural oxide layer. This process is referred to as a hydrogen plasma pre-cleaning process. Since the process is carried out under a low temperature, an excessive thermal budget is not caused contrary to a hydrogen baking process performed under a high temperature.
However, the semiconductor substrate may be damaged because of the hydrogen plasma pre-cleaning process depending on ion sputtering.